It is a BS call. Some foreigner who said he was IRS. When I said MY IRS agent speaks English, he got mad. I filed a complaint with the Attorney General's Office against them and was told the call is NOT originating from the USA. I then told him I might "deal" with him. I said in exchange for ______ (forgot, there may be kids here) then I won't file charges against you for impersonating an IRS officer. He got tongue tied and went off into some other language and hung up haha. Might as well have some fun at THEIR expense. I am thinking about ROBO calling them about 100 times in succession. That will at least keep them from calling out or receiving calls. Now to the software vault hahahahaha.
If they're leaving you messages, it is a response, no different than answering the call in person. NO kind of answer, you'll hear nothing from anyone you don't care to while getting on callers' nerves in the process.